1. Field of the Invention
The invention disclosed relates generally to lighting fixtures and in particular to heat dissipation in recessed lighting fixtures.
2. Discussion of the Related Art
Recessed lighting fixtures are designed to be minimally visible from below a ceiling in which they are mounted. LED light sources used for recessed lighting typically generate significant quantities of heat, requiring the use of a heat sink as part of the lighting fixture, to avoid overheating. The LED light source and an associated optic, are typically mounted in the heat sink so as to project light from the bottom of the heat sink. In some designs the heat sink may be supported in a mounting frame that is suspended by bar hangers fastened between joists above the ceiling. The mounting frame is positioned so that the bottom of the heat sink passes through an opening in the ceiling and is approximately flush with the bottom surface of the ceiling. A trim ring typically surrounds the opening in the ceiling, to mask the opening.
Directional LED recessed lighting fixtures are available, wherein a pivoted support or gimbal supports the heat sink and allows the rotation of the heat sink about a single axis. The directional or gimbal LED is typically capable of an adjustment range of from 0°-35° from vertical, for example. Conventionally, the heat sink containing the optic, is a rotatable inner heat sink that is pivotally mounted by gimbal supports within an outer heat sink. The inner heat sink is often the primary heat sink for the LED. Thus, it is an advantage to have the largest possible inner heat sink, to allow the LED to run at the coolest temperature possible.
An example directional or gimbal LED lighting fixture is described in U.S. Pat. No. 8,182,116, which depicts a heat sink that is pivotally mounted by gimbal supports within a much larger housing. The disclosed design does not enlarge the size of the heat sink to maximize its heat dissipation characteristics, since there is a large unused space shown within the housing.
Another example directional or gimbal LED lighting fixture is described in U.S. Pat. No. 8,403,533, which depicts an inner heat sink that is pivotally mounted by gimbal supports within an outer heat sink. The inner heat sink includes an arm that moves up into the outer heat sink for hinge tension and heat transfer. However the shape of the inner heat sink is not optimized to be as large as possible and yet still be capable of directional adjustment on its gimbal supports.
Accordingly, there is a need for a design of a rotatable inner heat sink for a directional or gimbal mounted LED recessed lighting fixture, which occupies a maximum available volume within an outer heat sink, and yet is still capable of directional adjustment on its gimbal supports.